Panel fuel injector

ABSTRACT

The present disclosure is directed to a panel fuel injector having a first side wall that defines a plurality of first side injection outlets and a second side wall that defines a plurality of second side injection outlets. A premix air plenum, a fuel plenum, a plurality of first side premixing channels and a plurality of second side premixing channels are defined between the first side wall and the second side wall. Each first side premixing channel is in fluid communication with the premix air plenum, the fuel plenum and a respective first side injection outlet of the plurality of first side injection outlets. Each second side premixing channel is in fluid communication with the premix air plenum, the fuel plenum and a respective second side injection outlet of the plurality of second side injection outlets.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims filing benefit of U.S. Provisional PatentApplication Ser. No. 62/313,232 having a filing date of Mar. 25, 2016,which is incorporated by reference herein in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with Government support under Contract No.DE-FE0023965 awarded by the United States Department of Energy. TheGovernment has certain rights in this invention.

FIELD OF DISCLOSURE

The present disclosure generally relates to a segmented combustionsystem for use in a gas turbine. More particularly, this disclosurerelates to a panel fuel injector for a segmented combustion system.

BACKGROUND

Industrial gas turbine combustion systems usually burn hydrocarbon fuelsand produce air polluting emissions such as oxides of nitrogen (NOx) andcarbon monoxide (CO). Oxidization of molecular nitrogen in the gasturbine depends upon the temperature of gas located in a combustor, aswell as the residence time for reactants located in the highesttemperature regions within the combustor. Thus, the amount of NOxproduced by the gas turbine may be reduced or controlled by eithermaintaining the combustor temperature below a temperature at which NOxis produced, or by limiting the residence time of the reactant in thecombustor.

One approach for controlling the temperature of the combustor involvespremixing fuel and air to create a fuel-air mixture prior to combustion.This approach may include the axial staging of fuel injectors where oneor more injectors are located at an upstream end of the combustor andone or more injectors are located at an axially downstream location. Theupstream injectors inject a first fuel-air mixture into a first orprimary combustion zone where it is ignited to produce a main flow ofhigh energy combustion gases. A second fuel-air mixture is injected intoand mixed with the main flow of high energy combustion gases via aplurality of radially oriented and circumferentially spaced fuelinjectors or axially staged fuel injector assemblies positioneddownstream from the primary combustion zone.

Axially staged injection increases the likelihood of complete combustionof available fuel, which in turn reduces the air polluting emissions.However, with conventional axially staged fuel injection combustionsystems there are various challenges with balancing air flow to thevarious combustor components, air flow requirements to the head end ofthe combustor for the first fuel-air mixture and/or compressed air flowto the axially staged fuel injectors for the second fuel-air mixturewhile maintaining emissions compliance over the full range of operationof the gas turbine. Therefore, an improved gas turbine combustion systemwhich includes axially staged fuel injection would be useful in theindustry.

BRIEF DESCRIPTION OF THE TECHNOLOGY

Aspects and advantages are set forth below in the following description,or may be obvious from the description, or may be learned throughpractice.

One embodiment of the present disclosure is directed to a panel fuelinjector. The panel fuel injector includes a first side wall thatdefines a plurality of first side injection outlets and a second sidewall that defines a plurality of second side injection outlets. A premixair plenum, a fuel plenum, a plurality of first side premixing channelsand a plurality of second side premixing channels are defined betweenthe first side wall and the second side wall. Each first side premixingchannel is in fluid communication with the premix air plenum, the fuelplenum and a respective first side injection outlet of the plurality offirst side injection outlets. Each second side premixing channel is influid communication with the premix air plenum, the fuel plenum and arespective second side injection outlet of the plurality of second sideinjection outlets.

Another embodiment of the present disclosure is directed to combustionsystem. The combustion system includes a first bundled tube fuel nozzle,a second bundled tube fuel nozzle that is circumferentially spaced fromthe first bundled tube fuel nozzle and a panel fuel injector disposedbetween the first bundled tube fuel nozzle and the second bundled tubefuel nozzle. The panel fuel injector includes a first side wall thatdefines a plurality of first side injection outlets and a second sidewall that defines a plurality of second side injection outlets. A premixair plenum, a fuel plenum, a plurality of first side premixing channelsand a plurality of second side premixing channels are defined betweenthe first side wall and the second side wall. Each first side premixingchannel and each second side premixing channel is in fluid communicationwith the premix air plenum and the fuel plenum.

Those of ordinary skill in the art will better appreciate the featuresand aspects of such embodiments, and others, upon review of thespecification.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the various embodiments, including thebest mode thereof to one skilled in the art, is set forth moreparticularly in the remainder of the specification, including referenceto the accompanying figures, in which:

FIG. 1 is a functional block diagram of an exemplary gas turbine thatmay incorporate various embodiments of the present disclosure;

FIG. 2 is an upstream view of an exemplary combustion section of a gasturbine, according to at least one embodiment of the present disclosure;

FIG. 3 provides a downstream or aft side view of a portion of anexemplary segmented annular combustion system, according to at least oneembodiment of the present disclosure;

FIG. 4 provides an upstream or forward side view of a portion of thesegmented annular combustion system as shown in FIG. 3, according to atleast one embodiment of the present disclosure;

FIG. 5 provides a perspective view of the portion of the exemplarysegmented annular combustion system of FIG. 3, according to at least oneembodiment of the present disclosure;

FIG. 6 provides a cross-sectioned perspective view of a portion of anexemplary bundled tube fuel nozzle taken along section line A-A as shownin FIG. 5, according to at least one embodiment of the presentdisclosure;

FIG. 7 provides a cross-sectioned side view of an annular combustionsystem mounted within an outer casing of a combustor, according tovarious embodiments of the present disclosure;

FIG. 8 provides a perspective view illustrating a first side wall of anexemplary panel fuel injector, according to at least one embodiment ofthe present disclosure;

FIG. 9 provides a perspective view of a second side wall of theexemplary fuel injection panel as shown in FIG. 8, according to at leastone embodiment of the present disclosure;

FIG. 10 provides a cross-sectioned top view of the exemplary panel fuelinjector taken along section line B-B as shown in FIG. 8, according toat least one embodiment of the present disclosure;

FIG. 11 provides a cross-sectioned top view of the exemplary panel fuelinjector taken along section line C-C as shown in FIG. 9, according toat least one embodiment of the present disclosure;

FIG. 12 provides a cross-sectioned top view of a bundled tube fuelnozzle and a pair of circumferentially adjacent panel fuel injectors,according to at least one embodiment of the present disclosure;

FIG. 13 provides a cross-sectioned top view of a bundled tube fuelnozzle and a pair of circumferentially adjacent panel fuel injectors,according to at least one embodiment of the present disclosure;

FIG. 14 provides a simplified perspective view of an exemplaryarrangement of panel fuel injectors and turbine nozzles, according to atleast one embodiment of the present disclosure;

FIG. 15 is an enlarged cross-sectioned top view of an arrangementbetween an exemplary panel fuel injector and a portion of an exemplarystationary nozzle, according to one or more embodiments of the presentdisclosure;

FIG. 16 provides a simplified perspective view of an exemplaryarrangement of panel fuel injectors and turbine nozzles, according to atleast one embodiment of the present disclosure;

FIG. 17 provides a top cross-sectioned perspective view of a portion ofan exemplary panel fuel injector, according to at least one embodimentof the present disclosure;

FIG. 18 provides a perspective view of an exemplary panel fuel injector,a bundled tube fuel nozzle, a portion of an inner liner and a portion ofan outer liner, according to at least one embodiment of the presentdisclosure;

FIG. 19 provides an enlarged cross-sectioned view of a portion of thepanel fuel injector as shown in FIG. 18, according to at least oneembodiment of the present disclosure;

FIG. 20 provides a perspective view of a portion of an exemplary panelfuel injector according to at least one embodiment of the presentdisclosure;

FIG. 21 provides a perspective view of a portion of an exemplarycombustor segment, according to at least one embodiment of the presentdisclosure;

FIG. 22 provides an illustration representing either a portion of anexemplary an inner liner or a portion of an exemplary outer liner,according to at least one embodiment of the present disclosure; and

FIG. 23 provides an illustration representing either a portion of anexemplary inner liner or a portion of an exemplary outer liner,according to at least one embodiment of the present disclosure.

DETAILED DESCRIPTION

Reference will now be made in detail to present embodiments of thedisclosure, one or more examples of which are illustrated in theaccompanying drawings. The detailed description uses numerical andletter designations to refer to features in the drawings. Like orsimilar designations in the drawings and description have been used torefer to like or similar parts of the disclosure.

As used herein, the terms “first”, “second”, and “third” may be usedinterchangeably to distinguish one component from another and are notintended to signify location or importance of the individual components.The terms “upstream” and “downstream” refer to the relative directionwith respect to fluid flow in a fluid pathway. For example, “upstream”refers to the direction from which the fluid flows, and “downstream”refers to the direction to which the fluid flows. The term “radially”refers to the relative direction that is substantially perpendicular toan axial centerline of a particular component, the term “axially” refersto the relative direction that is substantially parallel and/orcoaxially aligned to an axial centerline of a particular component andthe term “circumferentially” refers to the relative direction thatextends around the axial centerline of a particular component.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting. As used herein, thesingular forms “a”, “an” and “the” are intended to include the pluralforms as well, unless the context clearly indicates otherwise. It willbe further understood that the terms “comprises” and/or “comprising,”when used in this specification, specify the presence of statedfeatures, integers, steps, operations, elements, and/or components, butdo not preclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof.

Each example is provided by way of explanation, not limitation. In fact,it will be apparent to those skilled in the art that modifications andvariations can be made without departing from the scope or spiritthereof. For instance, features illustrated or described as part of oneembodiment may be used on another embodiment to yield a still furtherembodiment. Thus, it is intended that the present disclosure covers suchmodifications and variations as come within the scope of the appendedclaims and their equivalents.

Although exemplary embodiments of the present disclosure will bedescribed generally in the context of a segmented annular combustionsystem for a land-based power-generating gas turbine for purposes ofillustration, one of ordinary skill in the art will readily appreciatethat embodiments of the present disclosure may be applied to any type ofturbomachine and are not limited to annular combustion systems forland-based power-generating gas turbines unless specifically recited inthe claims.

Referring now to the drawings, FIG. 1 illustrates a schematic diagram ofan exemplary gas turbine 10. The gas turbine 10 generally includes aninlet section 12, a compressor 14 disposed downstream of the inletsection 12, a combustion section 16 disposed downstream of thecompressor 14, a turbine 18 disposed downstream of the combustionsection 16 and an exhaust section 20 disposed downstream of the turbine18. Additionally, the gas turbine 10 may include one or more shafts 22that couple the compressor 14 to the turbine 18.

During operation, air 24 flows through the inlet section 12 and into thecompressor 14 where the air 24 is progressively compressed, thusproviding compressed air 26 to the combustion section 16. At least aportion of the compressed air 26 is mixed with a fuel 28 within thecombustion section 16 and burned to produce combustion gases 30. Thecombustion gases 30 flow from the combustion section 16 into the turbine18, wherein energy (kinetic and/or thermal) is transferred from thecombustion gases 30 to rotor blades (not shown), thus causing shaft 22to rotate. The mechanical rotational energy may then be used for variouspurposes such as to power the compressor 14 and/or to generateelectricity. The combustion gases 30 exiting the turbine 18 may then beexhausted from the gas turbine 10 via the exhaust section 20.

FIG. 2 provides an upstream view of the combustion section 16, accordingto various embodiments of the present disclosure. As shown in FIG. 2,the combustion section 16 may be at least partially surrounded by anouter or compressor discharge casing 32. The compressor discharge casing32 may at least partially define a high pressure plenum 34 that at leastpartially surrounds various components of the combustion section 16. Thehigh pressure plenum 34 may be in fluid communication with thecompressor 14 (FIG. 1) so as to receive the compressed air 26 therefrom.

In various embodiments, as shown in FIG. 2, the combustion section 16includes a segmented annular combustion system 36. As shown in FIG. 2,the segmented annular combustion system 36 includes a series of fuelnozzles 100 and a corresponding series of hollow or semi-hollow panelfuel injectors 200 arranged in alternating fashion in an annular arrayabout an axial centerline 38 of the combustion section 16. The panelfuel injectors 200 extend radially (with respect to centerline 38)between an inner liner 300 and an outer liner 400, which form a radiallyinner and a radially outer combustion gas flow boundary within thecombustion section 16. The fuel nozzles 100 are disposed between theinner liner 300 and the outer liner 400, though not necessarilyextending across an entire radius therebetween.

FIG. 3 provides a downstream or aft side view of a portion of thesegmented annular combustion system 36, according to at least oneembodiment of the present disclosure. FIG. 4 provides an upstream orforward side view of a portion of the segmented annular combustionsystem 36, according to at least one embodiment of the presentdisclosure. In particular embodiments, as shown in FIGS. 3 and 4collectively, each panel fuel injector 200 circumferentially separatestwo circumferentially adjacent fuel nozzles 100. In the embodimentsillustrated herein, the fuel nozzles 100 are shown and described asbundled tube fuel nozzles, but it should be clear that other types offuel nozzles may be used instead. For example, one or more fuel nozzles(e.g., swozzles) or burners may be mounted in a cap face segment (notshown separately) that extends radially between the inner liner 300 andthe outer liner 400 and that extends circumferentially between adjacentpanel fuel injectors 200. Any reference to “bundled tube fuel nozzle100” is intended to encompass any type of fuel nozzle, unless contextdictates otherwise.

In particular embodiments, as shown in FIG. 3, a seal 40 such as afloating collar seal, spring seal, or hula seal may be attached to aside wall of one or more of the bundled tube fuel nozzles 100. Inparticular embodiments, as shown in FIG. 4, a seal 42 such as a floatingcollar seal, spring seal, or hula seal may be attached to a side wall ofone or more of the panel fuel injectors 200. The seals 40, 42 may beused to prevent, reduce and/or control air leakage between adjacentbundled tube fuel nozzles 100 and respective panel fuel injectors 200during operation of the combustion section 16.

In particular embodiments, as shown in FIGS. 2, 3 and 4 collectively,the segmented annular combustion system 36 may be subdivided intoindividual combustor segments 44. Each combustor segment 44 may includetwo or more (bundled tube) fuel nozzles 100 and at least one panel fuelinjector 200. In particular embodiments, as illustrated in FIGS. 2 and4, the inner liner 300 and/or the outer liner 400 may be subdivided intomultiple sections which correspond with one or more of the combustorsegments 44.

FIG. 5 provides a perspective view of an exemplary combustor segment 44,according to at least one embodiment of the present disclosure. Inparticular embodiments, as shown in FIG. 5, one or more of the combustorsegments 44 may be coupled to an end cover 46, which is formed to coupleto and/or seal against the compressor discharge casing 32 (FIG. 2) ofthe combustion section 16. In particular embodiments, the bundled tubefuel nozzles 100 may be fluidly coupled to the end cover 46 and/or afuel supply (not shown) via one or more fluid conduits 102. Inparticular embodiments, one or more of the panel fuel injectors 200 maybe fluidly coupled to the end cover 46 and/or a fuel supply (not shown)via one or more fluid conduits 202.

FIG. 6 provides a cross-sectioned perspective view of a portion of anexemplary bundled tube fuel nozzle 100, taken along section line A-A asshown in FIG. 5, according to at least one embodiment of the presentdisclosure. In various embodiments, as shown in FIG. 6, the bundled tubefuel nozzle 100 includes a housing body 104. The housing body 104includes a forward or upstream plate or face 106, an aft or downstreamplate or face 108, and an outer wall or shroud 110 that extends axiallyfrom and/or between the forward plate 106 and the aft plate 108 and thatmay define a radially outer perimeter of the bundled tube fuel nozzle100. A bundled tube fuel plenum 112 is defined within the housing body104. In particular embodiments, the bundled tube fuel plenum 112 may beat least partially defined by and/or between the forward plate 106, theaft plate 108, and the outer shroud 110.

As shown in FIG. 6, a plurality of tubes 114 extends axially through theforward plate 106, the bundled tube fuel plenum 112, and the aft plate108. Each tube 114 of the plurality of tubes 114 includes an inlet 116defined at or upstream from the forward plate 106 and an outlet 118defined at or downstream from the aft plate 108. Each of the tubes 114defines a respective premix passage 120 that extends between therespective inlet 116 and outlet 118. At least some of the tubes 114include or define at least one fuel port 122 in fluid communication withthe bundled tube fuel plenum 112. The fuel port(s) 122 provides forfluid communication from the bundled tube fuel plenum 112 into therespective premix passage 120 of the respective tube 114.

In operation, gaseous fuel (or in some embodiments, a liquid fuelreformed into a gaseous mixture) flows, via the fuel ports 122, from thebundled tube fuel plenum 112 into the respective premix passage 120 ofeach of the tubes 114, where the fuel mixes with air entering therespective inlet 116 of each tube 114. The fuel ports 122 may bepositioned along the respective tubes 114 in a single axial plane or inmore than one axial plane with respect to a centerline of the bundledtube fuel nozzle 100, for example, if a multi-tau arrangement is desiredto address or tune combustion dynamics between two adjacent primarycombustion zones 48 or to mitigate coherent axial modes between thesegmented annular combustion system 36 and the turbine 18.

In particular embodiments, the bundled tube fuel plenum 112 may besubdivided or partitioned via a wall or other feature (not shown) intotwo or more bundled tube fuel plenums 112 defined within the housingbody 104. In this embodiment, a first subset of tubes of the pluralityof tubes 114 may be fueled via a first bundled tube fuel plenum, and asecond subset of tubes of the plurality of tubes 114 may be fueledindependently via a second bundled tube fuel plenum. The bundled tubefuel nozzles 100 may be made as an integrated component, via casting oradditive manufacturing, to reduce costs and simplify assembly.

As shown in FIG. 6, the fluid conduit 102 may be coupled to and/orextend through the forward plate 106 and may provide for fluidcommunication into the bundled tube fuel plenum 112. In particularembodiments, as shown in FIG. 6, one or more of the bundled tube fuelnozzles 100 may include an inner tube 124 that extends axially withinthe respective fluid conduit 102 and through the respective aft plate108. The inner tube 124 may define a cartridge or air passage 126through the bundled tube fuel nozzle 100, which is capable of holding aliquid fuel cartridge, a sensor, an igniter, or some other component. Inparticular embodiments, the cartridge passage 126 may extend through theaft plate 108.

FIG. 7 provides a cross-sectioned side view of the annular combustionsystem 36 mounted within the compressor discharge casing 32 of thecombustion section 16, according to various embodiments of the presentdisclosure. As shown in FIG. 7, the inner liner 300, the outer liner400, and each respective panel fuel injector 200 at least partiallydefine a primary combustion chamber or zone 48 which is defineddownstream from a respective bundled tube fuel nozzle 100 of theplurality of bundled tube fuel nozzles 100. As shown in FIG. 2, theinner liner 300, the outer liner 400 and the plurality of panel fuelinjectors 200 define a plurality of annularly arranged primarycombustion zones 48 that are structurally and/or fluidly isolated withrespect to each other. An axial gap 50 is formed between an aft end 210of each panel fuel injector 200 and a leading edge (or forward portion)52 of a stationary nozzle 54 disposed proximate to an inlet of theturbine (FIG. 1). The secondary combustion zones 56 are unimpeded by thepanel fuel injectors 200 (that is, the secondary combustion zones 56 aredistributed within a portion of the annulus between the inner liner 300and the outer liner 400 downstream of the aft ends 210 of the panel fuelinjectors 200).

FIG. 8 provides a perspective view illustrating a first side wall 204 ofan exemplary panel fuel injector 200, according to at least oneembodiment of the present disclosure. FIG. 9 provides a perspective viewof a second side wall 206 of the exemplary fuel injection panel 200 asshown in FIG. 8, according to at least one embodiment of the presentdisclosure. As shown in FIGS. 8 and 9 collectively, each panel fuelinjector 200 includes a first side wall 204, a second side wall 206, aforward wall or upstream end portion 208, an aft or downstream end 210,a bottom (or radially inner) wall 212 and a top (or radially outer) wall214. The first side wall 204 and the second side wall 206 terminateand/or are interconnected at the aft end 210.

FIG. 10 provides a cross-sectioned top view, taken along section lineB-B as shown in FIG. 8, of the exemplary panel fuel injector 200,according to at least one embodiment of the present disclosure. FIG. 11provides a cross-sectioned top view, taken along section line C-C asshown in FIG. 9, of the panel fuel injector 200, according to at leastone embodiment of the present disclosure. As shown in FIGS. 10 and 11collectively, the first side wall 204 includes an outer (or hot) sidesurface 216 and an inner (or cold) side surface 218. As shown in FIGS.10 and 11 collectively, the second side wall 206 includes an outer (orhot) side surface 220 and an inner (or cold) side surface 222. The outerside surface 216 of the first side wall 204 and the outer side surface220 of the second side wall 206 are exposed to combustion gases duringoperation of the combustion system 36.

In various embodiments, as shown in FIGS. 8, 9, 10, and 11 collectively,each panel fuel injector 200 includes a premix air plenum or pocket 224(shown in hidden lines in FIGS. 8 and 9) and one or more fueldistribution plenums 226 (shown in hidden lines in FIGS. 8 and 9)defined within the respective panel fuel injector 200 between therespective first side wall 204 and the second side wall 206. As shown inFIGS. 8 and 9, the fuel distribution plenum 226 and/or the premix airplenum 224 may extend radially between the respective radially innerwall 212 and the radially outer wall 214. In particular embodiments, thefuel distribution plenum 226 may be in fluid communication with a fuelsupply (not shown) via the fluid conduit 202. In particular embodiments,as shown in FIG. 8, the fuel distribution plenum 226 may be in fluidcommunication with a fuel supply (not shown) via a fluid conduit orcoupling 228 that extends radially outwardly from the top wall 214and/or the bottom wall 212. Thus, the delivery of fuel 28 into the panelinjector wall 200 may occur in an axial direction or a radial direction,relative to the center line of the combustor 16.

In various embodiments, as shown in FIGS. 10 and 11 collectively, thepanel fuel injector 200 includes a plurality of premix channels that areradially stacked, that extend within the panel fuel injector 200 betweenthe first side wall 204 and the second side wall 206, and that are influid communication with the premix air plenum 224 and the fueldistribution plenum 226. In particular embodiments, the plurality ofpremix channels includes a plurality of first side premixing channels230 and a plurality of second side premixing channels 232 radiallystacked within the panel fuel injector 200 between the first side wall204 and the second side wall 206.

In particular embodiments, as shown in FIGS. 10 and 11, one or more ofthe first side premixing channels 230 extends axially along the innersurface 222 of the second side wall 206 and before curving partiallyaround the fuel distribution plenum 226 towards the first side wall 204where it terminates at a corresponding first side injection aperture 234defined along the first side wall 204. In particular embodiments, asshown in FIGS. 10 and 11, one or more of the second side premixingchannels 232 extends axially along the inner surface 218 of the firstside wall 204 and then curves partially around the fuel distributionplenum 226 towards the second side wall 206 where it terminates at acorresponding second side injection aperture 236 defined along thesecond side wall 206. For purposes of discussion herein, a “first side”premixing channel 230 is so-identified based on the side wall 204 onwhich its outlet (injection aperture 234) is located. Likewise, a“second side” premixing channel 232 is so-identified based on having anoutlet (injection aperture 236) on the second side wall 206.

In particular embodiments, the first side premixing channels 230 and/orthe second side premixing channels 232 may traverse or wind between thefirst side wall 204 and the second side wall 206 of the panel fuelinjector 200. In one embodiment, the first side premixing channels 230and/or the second side premixing channels 232 may traverse radiallyinwardly and/or outwardly between the first side wall 204 and the secondside wall 206 rather than along a straight or constant axial orlongitudinal plane of the panel fuel injector 200. The first sidepremixing channels 230 and/or the second side premixing channels 232 maybe oriented at different angles within the panel fuel injector 200. Inparticular embodiments, one or more of the first side premixing channels230 and/or the second side premixing channels 232 may be formed withvarying sizes and/or geometries. In particular embodiments, one or moreof the premixing channels 232, 234 may include a mixing-enhancingfeature therein, such as a bend, a kink, a twist, a helical portion,turbulators, or the like.

As shown in FIG. 11, each first side premixing channel 230 includes anair inlet 238, which is in fluid communication with the premix airplenum 224. In particular embodiments, one or more of the first sidepremixing channels 230 is in fluid communication with the fueldistribution plenum 226 via a respective fuel port 240. In variousembodiments, as shown in FIG. 8, the respective first side injectionapertures 234 are radially spaced and/or stacked along the first sidewall 204.

As shown in FIG. 10, each second side premixing channel 232 includes anair inlet 242, which is in fluid communication with the premix airplenum 224. In particular embodiments, one or more of the second sidepremixing channels 230 is in fluid communication with the fueldistribution plenum 226 via a respective fuel port 244. In variousembodiments, as shown in FIG. 9, the respective second side injectionapertures 236 are radially spaced and/or stacked along the second sidewall 206.

It is contemplated that the panel fuel injector 200 may have premixingchannels (230 or 232) that terminate in injection apertures locatedalong a single side wall (either the first side wall 204 or the secondside wall 206, respectively). Thus, while reference is made herein toembodiments having injection apertures 234, 236 on both the first sidewall 204 and the second side wall 206, it should be understood thatthere is no requirement that both the first side wall 204 and the secondside wall 206 have injection apertures 234, 236 for delivering afuel-air mixture unless recited in the claims. Additionally, theinjection apertures 234, 236 may be uniformly sized and spaced (asshown), or may be non-uniformly sized and/or spaced, as needs dictate.

In particular embodiments, the panel fuel injector 200 may be made as anintegrated or unitary component, via casting, additive manufacturing(such as by 3D printing techniques), or other similar manufacturingprocesses. By forming the panel fuel injector 200 as a unitary orintegrated component, the need for seals between the various features ofthe panel fuel injector 200 may be reduced or eliminated, part count andcosts may be reduced, and assembly steps may be simplified oreliminated. In other embodiments, the panel fuel injector 200 may befabricated, such as by welding, or may be formed from differentmanufacturing techniques, where components made with one technique arejoined to components made by another technique. In particularembodiments, at least a portion or all of each panel fuel injector 200may be formed from a ceramic matrix composite (CMC) or other compositematerial.

FIG. 12 provides a cross-sectioned top view of a portion of the annularcombustion system 36 including one bundled tube fuel nozzle 100 of theplurality of bundled tube fuel nozzles 100 and a pair ofcircumferentially adjacent panel fuel injectors 200 of the plurality ofpanel fuel injectors 200, according to various embodiments of thepresent disclosure. As shown in FIG. 12, each respective primarycombustion zone 48 is defined upstream from the corresponding first sideinjection apertures 234 and second side injection apertures 236 of apair of circumferentially adjacent panel fuel injectors 200. As shown inFIG. 12, a secondary combustion zone 56 is defined downstream from thecorresponding first side injection apertures 234 and second sideinjection apertures 236 of the pair of circumferentially adjacent panelfuel injectors 200.

As shown in FIG. 12, the first side injection apertures 234 and thesecond side injection apertures 236 of two circumferentially adjacentfuel injection panels 200 of the plurality of panel fuel injectors 200define respective first side and second side injection plane(s) 58, 60,respectively, from which a second fuel and air mixture is injected intoa flow of combustion gases originating from the respective primarycombustion zone 48. The first side injection plane 58 is defined at afirst axial distance 62 from the aft plate 108 of the respective bundledtube fuel nozzle 100. The second side injection plane 60 is defined at asecond axial distance 64 from the aft plate 108 of the respectivebundled tube fuel nozzle 100.

In particular embodiments (such as the embodiment shown in FIG. 12), thefirst axial distance 62 of the first side injection plane 58 and thesecond axial distance 64 of the second side injection plane 60 may becoincident (i.e., at the same axial distance from the aft plate 108 ofthe respective bundled tube fuel nozzle 100). In other embodiments (suchas the embodiment shown in FIG. 13), the first side injection plane 58and the second side injection plane 60 may be defined or axially stagedat different axial distances from the aft plate 108 of the respectivebundled tube fuel nozzle 100 (i.e., the first axial distance 62 isdifferent from the second axial distance 64).

Although the plurality of first side injection apertures 234 are shownin FIG. 8 in a common radial or injection plane 58, in some embodiments,one or more of the first side injection apertures 234 may be staggeredaxially with respect to radially adjacent first side injection apertures234, thereby off-setting the axial distance 60 of one or more of thefirst side injection apertures 234. Similarly, although the plurality ofsecond side injection apertures are shown in FIG. 9 in a common radialor injection plane 60, in some embodiments, one or more of the secondside injection apertures 236 may be staggered axially with respect toradially adjacent second side injection apertures 236, therebyoff-setting the axial distance 62 of one or more of the second sideinjection apertures 236. The amount of off-set of the first sideinjection apertures 234 may be different from the amount of off-set ofthe second side injection apertures 236.

FIG. 13 provides a cross-sectioned top view of a portion of the annularcombustion system 36 including one bundled tube fuel nozzle 100 of theplurality of bundled tube fuel nozzles 100 and a pair ofcircumferentially adjacent panel fuel injectors 200 of the plurality ofpanel fuel injectors 200, according to various embodiments of thepresent disclosure. In particular embodiments, the aft end 210(a) of afirst panel fuel injector 200(a) of the plurality of panel fuelinjectors 200 may be positioned axially downstream, with respect to theaft plate 108 of a respective bundled tube fuel nozzle 100, from the aftend 210(b) of a second panel fuel injector 200(b) of the plurality ofpanel fuel injectors 200. In other words, an axial gap 50(a) definedbetween the aft end 210(a) of the panel fuel injector 200(a) and aleading edge 52(a) of a stationary nozzle 54(a) may be smaller than anaxial gap 50(b) defined between the aft end 210(b) of panel fuelinjector 200(b) and a leading edge 52(b) of a second stationary nozzle54(b).

Referring again to FIG. 12, during axially staged operation of thecombustion system 36, a portion of the compressed air 26 from thecompressor 14 flows through the inlets 116 of the tubes 114 of thebundled tube fuel nozzles 100 while fuel 28 is supplied to therespective fuel plenums 112. The fuel 28 is injected via fuel ports 122into the flow of compressed air within the tubes 114. The fuel and airmix within each tube 114 to provide a primary fuel-air mixture to theprimary combustion zone 48. The primary fuel-air mixture is burned inthe primary combustion zone 48 to produce a hot effluent stream ofcombustion gases. In the case of the exemplary bundled tube fuel nozzles100 illustrated herein, relatively short flames originate from theoutlets 118 of each of the tubes 114 in each corresponding primary (orfirst) combustion zone 48. The hot effluent stream flows downstreamtowards the first side injection plane 58 and the second side injectionplane 60.

A portion of the compressed air 26 is routed into the premix air plenum224 of the panel fuel injectors 200. The compressed air 26 is routedfrom the premix air plenum 224 into the respective inlet 238 of each ofthe first side premixing channels 230 and into the respective inlet 242of each second side premixing channels 232. Fuel 28 is supplied to thefuel distribution plenum 226 via fluid conduit 202 and/or fluid conduit228. As the compressed air 26 flows through the first side premixingchannels 230 and the second side premixing channels 232 of therespective panel fuel injectors 200, the fuel may be injected into thefirst side premixing channels 230 via respective fuel ports 240 and/orinto each of the second side premixing channels 232 via fuel ports 244.

The fuel and air mix within the first side premixing channels 230 of afirst panel fuel injector 200 to provide a first premixed stream of fueland air to the first side injection plane 58 via the first sideinjection apertures 234. The fuel and air mix within the second sidepremixing channels 232 of a circumferentially adjacent panel fuelinjector 200 to provide a second premixed stream of fuel and air to thesecond side injection plane 60 via the second side injection apertures236. In at least one embodiment, it may be desirable to have thesecondary fuel and air introduction occur from a single side (e.g., thefirst side wall 204 or the second side wall 206) of the panel fuelinjector 200. The first side injection apertures 234 and/or the secondside injection apertures 236 may be arranged in one or more radial oraxial planes.

The hot effluent stream and the first and second premixed streams offuel and air react in the secondary combustion zone 56. The hot effluentstream from the primary combustion zone 48, approximately 40% to 95% oftotal combustion gas flow, accelerates until reaching the injectionplanes 58 and/or 60, where the balance of fuel and air flow, via thefirst and second premixed streams, is added into the secondarycombustion zone 56. In one embodiment, approximately 50% of totalcombustion gas flow originates from the primary combustion zone 48, andthe remaining approximately 50% originates from the secondary combustionzone 56. This arrangement enables sufficient time to achieve COconversion to CO2 and to minimize NOx formation at the lowertemperatures of the primary combustion zone and prior to the elevatedgas temperatures that occur between the first and second side injectionplanes 58, 60 and the stationary nozzle 54, thereby minimizing overallNOx emissions.

Circumferential dynamics modes are common in traditional annularcombustors. However, largely due to axially staged secondary fuel-airinjection, the segmented annular combustion system 36 described andillustrated herein does not allow these dynamic modes to exist. Further,because each combustor segment is isolated from circumferentiallyadjacent segments, multi-can dynamics is mitigated or non-existent.

During operation of the segmented annular combustion system 36, it maybe necessary to cool one or more of the first side wall 204, the secondside wall 206, the stationary nozzle 54, the inner liner 300 and/or theouter liner 400 in order to enhance mechanical performance of theindividual components. In order to accommodate cooling requirements, oneor more of the first side wall 204, the second side wall 206, thestationary nozzle 54, the inner liner 300 and/or the outer liner 400 mayinclude various air passages or cavities, which may be in fluidcommunication with the high pressure plenum 34 formed within thecompressor discharge casing 32 and/or with the premix air plenum 224defined within each panel fuel injector 200.

In particular embodiments, as shown in FIG. 12, one or more of the fuelports 244 may be angled, shaped or formed so as to impinge or direct ajet of fuel 28 from the fuel distribution plenum 226 onto the innersurface 218 of the first side wall 204, thereby providing impingementcooling thereto. In particular embodiments, the compressed air 26flowing from the premix air plenum 224 may provide convective cooling tothe inner surface 218 of the first side wall 204.

In particular embodiments, as shown in FIG. 12, one or more of the fuelports 240 may be angled, shaped or formed so as to impinge or direct ajet of fuel 28 from the fuel distribution plenum 226 onto the innersurface 222 of the second side wall 206, thereby providing impingementcooling thereto.

As shown in FIG. 12, a cooling air cavity or pocket 246 may be definedwithin the panel fuel injector 200 between the first side wall 204 andthe second side wall 206. One or more ports 248 may be angled, shaped orformed so as to impinge or direct a jet of compressed air 26 from thecooling air cavity 246 onto the inner surface 218 of the premixingchannel 232. In the exemplary embodiment shown, the inner surface 218 ofthe premixing channel 232 is coincident with the first side wall 204,thereby providing impingement cooling thereto.

In particular embodiments, the compressed air 26 flowing from the premixair plenum 224 may provide convective cooling to the inner surface 222of the second side wall 206. One or more ports 250 may be angled, shapedor formed so as to impinge or direct a jet of compressed air 26 from thecooling air cavity 246 onto the inner surface 222 of the premixingchannel 230. In the exemplary embodiment shown, the inner surface 222 ofthe premixing channel 230 is coincident with the second side wall 206,thereby providing impingement cooling thereto.

FIG. 12 also illustrates that the fuel distribution plenum 226 isflanked on an upstream side by the cooling air cavity 246 and on thedownstream side by a continuation of the cooling air cavity 246.Downstream of the fuel port 240, 244, the premixing channels 230, 232include a curved end section that directs the fuel/air mixture to therespective injection aperture 234, 236. The curved end section includesan inner radius and an outer radius. Ports 248 may be provided in theinner radius of the curved portion, the ports 248 being in fluidcommunication with the downstream portion of the cooling air cavity 246,to direct a film of air along an interior surface of the curved portionof the premixing channel 230, 232, thereby preventing the flow fromstagnating along the wall of the premixing channel 232, 234.

FIG. 14 is a simplified perspective view of an exemplary combustorsegment 44, according to at least one embodiment of the presentdisclosure. FIG. 15 is an enlarged cross-sectioned top view of anexemplary panel fuel injector 200 and includes a portion of an exemplarystationary nozzle 54, according to one or more embodiments of thepresent disclosure. In particular embodiments, as shown in FIGS. 14 and15 collectively, the aft end 210 of at least one panel fuel injector 200is disposed proximate, adjacent, immediately adjacent or next to arespective leading edge 52 of a respective stationary nozzle 54. Assuch, the respective axial gap 50 defined between the aft end 210 of thepanel fuel injector 200 and the leading edge 52 of the respectivestationary nozzle 54 is minimalized, thereby at least partiallyshielding the respective leading edge 52 from the flow of combustiongases 30. For example, the axial gap 50 between the aft end 210 and theleading edge of a respective stationary nozzle 54 may be less than sixinches, less than three inches, less than two inches, or less than oneinch. Further, in these embodiments, the secondary combustion zones 56are separated from one another, and the number of secondary combustionzones 56 is equal to the number of primary combustion zones 48.

In particular embodiments, as shown in FIG. 14, the aft end at least oneof the first side wall 204 and the second side wall 206 may extendaxially past the leading edge 52 towards the trailing edge and/orpartially across a pressure side wall 66 or a suction side wall 68 ofthe stationary nozzle 54, thereby at least partially shielding a portionof the pressure side wall 66 and/or the suction side wall 68 from theflow of combustion gases 30.

In particular embodiments, as shown in FIG. 15, at least one panel fuelinjector 200 includes a cooling air plenum 252 defined between the firstside wall 204 and the second side wall 206 proximate to the aft end 210.An aft wall 254 or the aft end 210 of the panel fuel injector 200 may bearcuate or concave or otherwise complementary in shape to the leadingedge 52 of a respective stationary nozzle 54. For example, the aft end210 of the panel fuel injector 200 may define a pocket or slot, and theleading edge 52 of the stationary nozzle 54 may extend into the pocket.One or more cooling holes 256 may be defined along the aft wall 254. Thecooling holes 256 are in fluid communication with the cooling air plenum252. During operation, compressed air 26 may flow from the cooling airplenum 252, though the cooling holes 256 and into the axial gap 50,thereby providing at least one of impingement and film cooling to thecorresponding stationary nozzle 54, particularly to the leading edge 52of the corresponding stationary nozzle 54.

Alternately, as shown in FIG. 16, the combustor 36 may include a firstset of panel fuel injectors 200 a that define a first axial gap 50 abetween a respective aft end 210 and a corresponding stationary nozzle54 (“short” panel fuel injectors, as in FIG. 7) and a second set ofpanel fuel injectors 200 b that define a second axial gap 50 b between arespective aft end 210 and a corresponding stationary nozzle 54 (“long”panel fuel injectors, as in FIG. 14). The number of panel fuel injectors200 b in the second set may be smaller than the number of panel fuelinjectors 200 a in the first set. In some embodiments, the panel fuelinjectors 200 b in the second set are spaced circumferentially apartfrom one another (i.e., are not adjacent). In this exemplaryconfiguration, which may be useful for mitigating dynamics, the numberof secondary combustion zones 56 is smaller than the number of primarycombustion zones 48. That is, the secondary combustion zones 56 areformed axially downstream of the aft ends 210 of the panel fuelinjectors 200 a in the first set and extend circumferentially betweenthe panel fuel injectors 200 b of the second set.

FIG. 17 provides a top cross-sectioned perspective view of a portion ofan exemplary panel fuel injector 200, according to at least oneembodiment of the present disclosure. In particular embodiments, asshown in FIG. 17, the first side wall 204 may define a plurality offirst side micro-cooling channels 258 that extend between and/or isdefined between the inner surface 218 and the outer surface 216 of thefirst side wall 204. Each first side micro-cooling channel 258 includesa respective inlet 260 and a respective outlet 262. The respective inlet260 to one or more of the first side micro-cooling channels 258 may bein fluid communication with the cooling air plenum 252, the cooling aircavity 246, the premix air plenum 223 or other compressed air or coolingfluid source. The respective outlet 262 of one or more of the first sidemicro-cooling channels 258 may be defined along the aft wall 254 of thepanel fuel injector 200. Although the first side micro-cooling channels258 are shown as extending substantially axially or linearly through thefirst side wall 204, it should be noted that one or more of the firstside micro-cooling channels 258 may extend between the inner surface 218and the outer surface 216 in a serpentine or curved pattern.

In particular embodiments, as shown in FIG. 17, the second side wall 206may define a plurality of second side micro-cooling channels 264 thatextend between the inner surface 222 and the outer surface 220 of thesecond side wall 206. Each second side micro-cooling channel 264includes a respective inlet 266 and a respective outlet 268. Therespective inlet 266 to one or more of the second side micro-coolingchannels 264 may be in fluid communication with the cooling air plenum252, the cooling air cavity 246, the premix air plenum 224 (FIG. 15) orother compressed air or cooling fluid source. The respective outlet 268of one or more of the second side micro-cooling channels 264 may bedefined along the aft wall 254 of the panel fuel injector 200. Althoughthe second side micro-cooling channels 264 are shown as extendingsubstantially axially or linearly through the second side wall 206, itshould be noted that one or more of the second side micro-coolingchannels 264 may extend between the inner surface 222 and the outersurface 220 in a serpentine or curved pattern.

In particular embodiments, as shown in FIG. 17, a wall thickness T ofeither or both of the first side wall 204 and the second side wall 206of the panel fuel injector 200 may vary along the axial or longitudinallength and/or along a radial span of the panel fuel injector 200. Forexample, the wall thickness of either or both of the first side wall 204and the second side wall 206 of the panel fuel injector 200 may varybetween the upstream end portion 208 and the aft end 210 and/or betweenthe radially inner wall 212 and the radially outer wall 214 (FIG. 9).

In particular embodiments, as illustrated in FIG. 17, an overallinjection panel thickness PT may vary along the axial or longitudinallength and/or along a radial span of the panel fuel injector 200. Forexample, the first side wall 204 and/or the second side wall 206 maybulge outwardly towards and/or into the flow of combustion gases flowingbetween two circumferentially adjacent panel fuel injectors 200. Thebulge or variation in overall injection panel thickness PT may occur atany point along the radial span and/or the axial length of therespective first side wall 204 or the second side wall 206. Panelthickness PT or the position of the bulged region may vary along theaxial length and/or the radial span of first side wall 204 or the secondside wall 206 the passage to tailor the local hot passage areas toachieve a certain target velocity and residence time profile withoutrequiring a change in wall thickness T.

FIG. 18 provides a perspective view of an exemplary panel fuel injector200, bundled tube fuel nozzle 100, a portion of the inner liner 300 anda portion of the outer liner 400, according to at least one embodimentof the present disclosure. FIG. 19 provides an enlarged cross-sectionedview of a portion of the panel fuel injector 200 as shown in FIG. 17,according to at least one embodiment. In particular embodiments, asshown in FIGS. 18 and 19 collectively, at least one of the panel fuelinjectors 200 may define at least one cross-fire opening 270 thatextends through the first side wall 204 and the second side wall 206 ofthe respective panel fuel injector 200. The cross-fire opening 270permits cross-fire and ignition of circumferentially adjacent primarycombustion zones 48.

In one embodiment, the cross-fire opening 270 is defined by adouble-walled cylindrical structure with an air volume therebetween. Thecombustion gases 30, ignited in a first combustion zone 48, arepermitted to flow through the inner wall of the cross-fire opening 270into an adjacent primary combustion zone 48, where ignition of the fueland air mixture in the adjacent primary combustion zone 48 occurs. Toprevent combustion gases 30 from stagnating in the cross-fire opening70, purge air holes 272 are provided in the inner wall. In addition topurge air holes 272, the outer walls of the cross-fire openings 270 maybe provided with air feed holes 273 that may be in fluid communicationwith at least one of the premix air plenum 224, the cooling air cavity246, or another compressed air source. The purge air holes 272 are influid communication with the air volume, which receives air via the airfeed holes 273. The combination of smaller air feed holes 273 in theouter wall and larger purge air holes 272 in the inner wall transformsthe cross-fire opening 270 into a resonator for mitigating potentialcombustion dynamics within the segmented annular combustion system 36.

FIG. 20 provides a perspective view of a portion of an exemplary panelfuel injector 200, according to at least one embodiment. In particularembodiments, as shown in FIG. 20, at least one impingement air insert274, 276 may be disposed within a respective air cavity such as thecooling air cavity 246 and/or the cooling air plenum 252 defined withina respective panel fuel injector 200 of the plurality of panel fuelinjectors 200. The impingement air inserts 274, 276 include walls thatare complementary in shape to the cooling air cavity 246 and cooling airplenum 252, respectively. The impingement air inserts 274, 276 includeat least one open end through which air may flow. At least one of theimpingement air insert(s) 274, 276 may include or define a plurality ofcooling or impingement holes 278, 280 oriented and/or formed to directmultiple discrete jets of air onto one or more inner surfaces 218, 222(FIGS. 10 & 11) of the respective panel fuel injector 200 at discretelocations to provide jetted or impingement cooling thereto.

FIG. 21 provides a perspective view of a portion of an exemplarycombustor segment 44, according to at least one embodiment of thepresent disclosure. In particular embodiments, as shown in FIG. 21, theinner liner 300 and the outer liner 400 are double-banded structures,each defining a respective flow annulus between an inner band and anouter band. In these embodiments, the inner liner 300 and the outerliner 400 are cooled by impingement and/or film cooling.

Specifically, in these embodiments, the inner liner 300 includes aninner band 302 that is radially spaced from an outer band 304. In atleast one embodiment, a wall 306 extends radially between the inner band302 and the outer band 304. The inner band 302, the outer band 304, andthe wall 306 (when present) define an inner flow annulus 308therebetween.

In particular embodiments, an inlet 310 to the inner flow annulus 308 isdefined at a downstream end of the inner liner 300. In particularembodiments, the inner flow annulus 308 is in fluid communication withthe compressor 16 via the high pressure plenum 34 and the inlet 310. Inparticular embodiments, the outer band 304 may define a plurality ofapertures 312. In operation, the apertures 312 provide for fluidcommunication between the high pressure plenum 34 and the inner flowannulus 308. In particular embodiments, one or more apertures 312 of theplurality of apertures 312 is oriented to direct jets of cooling airagainst a cool side surface 313 of the inner band 302 of the inner liner300.

In particular embodiments, the inner band 302 defines a primary aperture314. In operation, the primary aperture 314 provides for fluidcommunication between the inner flow annulus 308 and a respective panelfuel injector 200. For example, in particular embodiments, the primaryaperture 312 may provide for compressed air flow between the inner flowannulus 308 and one or more of the premix air plenum 224, the coolingair cavity 246 and the cooling air plenum 252. In particularembodiments, the inner band 302 may define a plurality of secondaryapertures 316. During operation, compressed air 26 from the inner flowannulus 308 may flow through the secondary apertures 316, therebyproviding a cooling film of the compressed air 26 across an outer or hotside surface 318 of the inner band 302.

In particular embodiments, as shown in FIG. 21, the outer liner 400includes an inner band 402 that is radially spaced from an outer band404. In at least one embodiment, a wall 406 extends radially between theinner band 402 and the outer band 404. The inner band 402, the outerband 404, and the wall 406 (when present) define an outer flow annulus408 therebetween. In particular embodiments, an inlet 410 to the outerflow annulus 408 is defined at a downstream end of the outer liner 400.In particular embodiments, the outer flow annulus 408 is in fluidcommunication with the compressor 16 via the high pressure plenum 34 andthe inlet 410. In particular embodiments, the outer band 404 may definea plurality of apertures 412. In operation, the apertures 412 providefor fluid communication between the high pressure plenum 34 and theouter flow annulus 408. In particular embodiments, one or more apertures412 of the plurality of apertures 412 is oriented to direct jets ofcooling air against a cool side surface of the inner band 402 of theouter liner 400.

In particular embodiments, the inner band 402 defines a primary aperture414. In operation, the primary aperture 414 provides for fluidcommunication between the outer flow annulus 408 and a respective panelfuel injector 200. For example, in particular embodiments, the primaryaperture 414 may provide for compressed air flow between the outer flowannulus 408 and one or more of the premix air plenum 224, the coolingair cavity 246, and the cooling air plenum 252. In particularembodiments, the inner band 402 may define a plurality of secondaryapertures 416. During operation, compressed air 26 from the outer flowannulus 408 may flow through the secondary apertures 416, therebyproviding a cooling film of the compressed air 26 across an inner or hotside surface 418 of the inner band 402.

FIGS. 22 and 23 are intended to be illustrative of a portion of eitheror both the inner band 302 of the inner liner 300 or the inner band 402of the outer liner 400, according to particular embodiments of thepresent disclosure. In these embodiments, the inner liner 300 and theouter liner 400 are single-wall structures through which micro-channelcooling passages are disposed, as described below. Thus, the cooling ofthe inner liner 300 and the outer liner 400 is accomplished viaconvective cooling, rather than impingement and/or film cooling asdescribed with reference to FIG. 21.

In particular embodiments, as shown in FIGS. 22 and 23, the outer orcool side surface of the inner liner 300 and/or the outer or cool sidesurface 413 of the outer liner 400 may define or include a plurality ofinlet holes 320, 420 for receiving compressed air 26 from thehigh-pressure plenum 34 (FIG. 2). Each inlet hole 320, 420 may beintegrated with a micro-channel cooling passage 322, 422 that terminatesat a corresponding outlet hole or exhaust port 324, 424. The length ofthe micro-channel cooling passages 322, 422 may vary in different areasof the liner 300, 400.

In particular embodiments, the length of some or all of themicro-channel cooling passages 322, 422 may be less than about teninches. In particular embodiments, the length of some or all of themicro-channel cooling passages 322, 422 may be less than about fiveinches. In particular embodiments, the length of some or all of themicro-channel cooling passages 322, 422 may be less than about twoinches. In particular embodiments, the length of some or all of themicro-channel cooling passages 322, 422 may be less than about one inch.In particular embodiments, one or more of the micro-channel coolingpassages 322, 422 may be between 0.5 inches and 6 inches. The length ofthe various micro-channel cooling passages 322, 422 may be determined bythe heat pick-up capability of the air flowing therethrough (i.e., thetemperature of the cooling air), the diameter of the micro-channelpassage, and the temperature of the liner 300, 400 in the area to becooled.

In particular embodiments, one or more of the outlet holes 324, 424 maybe located along the respective outer surface 318, 418 and may depositthe compressed air 26 from the respective inlet holes 320, 420 into arespective flow passage or collection channel 326, 426. In at least oneembodiment, as shown in FIG. 22, the collection channel 326, 426 may bedefined by a duct 328, 428 that extends along the respective outersurface 318, 418. The respective collection channel 326, 426 may conveyat least a portion of the compressed air 26 to the premix air plenum 224(FIG. 12) of the panel fuel injector 200 where it may be distributed tothe various first side premixing channels 230 and/or the second sidepremixing channels 232. More details about micro-channel cooling usingthis approach are described in commonly assigned U.S. patent applicationSer. No. 14/944,341, filed Nov. 18, 2015.

In particular embodiments, one or more of the micro-channel coolingpassages 322, 422 may be oriented so as to provide for compressed airflow between one or more of the premix air plenum 224, the cooling aircavity 246 and the cooling air plenum 252. Thus, the compressed air 26from one or more of the micro-channel cooling passages 322, 422 may bemixed with the compressed air 26 that is used to cool the interior ofthe panel fuel injector 200.

In particular embodiments, it is possible to use micro-channel coolingand impingement cooling. For example, the outlet holes 324, 424 of oneor more of the micro-channel cooling passages 322, 422 may be locatedalong a side wall 325, 425 (FIG. 21) of the inner band 302 or the innerband 402, such that the compressed air 26 flows through themicro-channel cooling passages 322, 422 and then between twocircumferentially adjacent inner liners 300 or adjacent outer liners 400along a split line defined between the two adjacent inner or outerliners 300, 400, thereby creating a fluid seal therebetween. In oneembodiment, the outlet holes 324, 424 of one or more of themicro-channel cooling passages 322, 422 may be located along therespective hot side surface 318 of the inner band 302 or the hot sidesurface 418 of the outer band 404, such that the compressed air 26 flowsthrough the micro-channel cooling passages 322, 422 and then enterseither the primary or the secondary combustion chambers or zones 48, 56as cooling film air.

The various embodiments of the segmented annular combustion system 36,particularly the bundled tube fuel nozzles 100 in combination with thepanel fuel injectors 200, the inner liner 300, and outer liner 400described and illustrated herein provide various enhancements orimprovements to the operations and turndown capability over conventionalannular combustion systems. For example, during start-up of thesegmented annular combustion system 36, the igniters may ignite the fueland air mixture flowing from the outlets 118 of the tubes 114 of theplurality of tubes 114. As power needs increase, fuel to the panel fuelinjectors 200 may be turned on simultaneously or sequentially until eachpanel fuel injector 200 is operational.

To reduce power output, the fuel flowing to the tubes 114 of the bundledtube fuel nozzles 100 and/or to the panel fuel injectors 200 may bethrottled down simultaneously or sequentially as desired. When itbecomes desirable or necessary to turn off the panel fuel injectors 200,the fuel may be shut off to each panel fuel injector 200 or toindividual panel fuel injectors 200 or groups of the panel fuelinjectors 200, thereby minimizing any disturbance to the turbineoperation.

This written description uses examples to disclose the invention,including the best mode, and to enable any person skilled in the art topractice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they include structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal language of the claims.

What is claimed is:
 1. A panel fuel injector, comprising: a first sidewall defining a plurality of first side injection outlets; a second sidewall defining a plurality of second side injection outlets; and a premixair plenum, a fuel plenum, a plurality of first side premixing channelsand a plurality of second side premixing channels defined between thefirst side wall and the second side wall; wherein each first sidepremixing channel is in fluid communication with the premix air plenum,the fuel plenum and a respective first side injection outlet of theplurality of first side injection outlets; wherein each second sidepremixing channel is in fluid communication with the premix air plenum,the fuel plenum and a respective second side injection outlet of theplurality of second side injection outlets; and wherein a portion of atleast one first side premixing channel extends along an inner surface ofthe second side wall.
 2. The panel fuel injector as in claim 1, furthercomprising a cooling air cavity defined between the first side wall andthe second side wall.
 3. The panel fuel injector as in claim 2, furthercomprising an impingement air insert disposed within the cooling aircavity.
 4. The panel fuel injector as in claim 2, wherein at least onefirst side premixing channel includes a curved portion proximate arespective first side injection outlet, the curved portion having anouter radius, an inner radius, and a port defined in the inner radius,wherein the port provides for fluid communication from the cooling aircavity into the at least one first side premixing channel along theinner radius.
 5. The panel fuel injector as in claim 1, furthercomprising a cooling air plenum defined between the first side wall andthe second side wall proximate to a downstream end portion of the panelfuel injector.
 6. The panel fuel injector as in claim 5, furthercomprising an impingement air insert disposed within the cooling airplenum.
 7. The panel fuel injector as in claim 1, wherein at least aportion of one or more first side premixing channels is at leastpartially defined by an inner surface of the second side wall.
 8. Thepanel fuel injector as in claim 1, wherein a portion of at least onesecond side premixing channel extends along an inner surface of thefirst side wall.
 9. The panel fuel injector as in claim 8, wherein atleast a portion of one or more second side premixing channels is atleast partially defined by an inner surface of the first side wall. 10.A combustion system, comprising: a first fuel nozzle; a second fuelnozzle circumferentially spaced from the first fuel nozzle; and a panelfuel injector disposed between the first fuel nozzle and the second fuelnozzle, the panel fuel injector comprising: a first side wall defining aplurality of first side injection outlets; a second side wall defining aplurality of second side injection outlets; a premix air plenum, a fuelplenum, a plurality of first side premixing channels, and a plurality ofsecond side premixing channels defined between the first side wall andthe second side wall; a cooling air cavity defined between the firstside wall and the second side wall; wherein each first side premixingchannel is in fluid communication with the premix air plenum, the fuelplenum, and a respective first side injection outlet of the plurality offirst side injection outlets; wherein each second side premixing channelis in fluid communication with the premix air plenum, the fuel plenum,and a respective second side injection outlet of the plurality of secondside injection outlets; and wherein at least one first side premixingchannel includes a curved portion proximate a respective first sideinjection outlet, the curved portion having an outer radius, an innerradius, and a port defined in the inner radius, wherein the portprovides for fluid communication from the cooling air cavity into the atleast one first side premixing channel along the inner radius.
 11. Thecombustion system as in claim 10, further comprising an impingement airinsert disposed within the cooling air cavity.
 12. The combustion systemas in claim 10, further comprising a cooling air plenum defined betweenthe first side wall and the second side wall proximate to a downstreamend portion of the panel fuel injector.
 13. The combustion system as inclaim 12, further comprising an impingement air insert disposed withinthe cooling air plenum.
 14. The combustion system as in claim 10,wherein a portion of at least one first side premixing channel of theplurality of first side premixing channels extends along an innersurface of the second side wall.
 15. The combustion system as in claim14, wherein at least a portion of one or more first side premixingchannels of the plurality of first side premixing channels is at leastpartially defined by an inner surface of the second side wall.
 16. Thecombustion system as in claim 10, wherein a portion of at least onesecond side premixing channel of the plurality of second side premixingchannels extends along an inner surface of the first side wall.
 17. Thecombustion system as in claim 16, wherein at least a portion of one ormore second side premixing channels of the plurality of second sidepremixing channels is at least partially defined by an inner surface ofthe first side wall.
 18. A panel fuel injector, comprising: a first sidewall defining a plurality of first side injection outlets; a second sidewall defining a plurality of second side injection outlets; a premix airplenum defined between the first side wall and the second side wall; afuel plenum defined between the first side wall and the second sidewall; a plurality of first side premixing channels defined between thefirst side wall and the second side wall, each first side premixingchannel in fluid communication with the premix air plenum, the fuelplenum, and a respective first side injection outlet of the plurality offirst side injection outlets; a plurality of second side premixingchannels defined between the first side wall and the second side wall,each second side premixing channel in fluid communication with thepremix air plenum, the fuel plenum, and a respective second sideinjection outlet of the plurality of second side injection outlets; acooling air cavity defined between the first side wall and the secondside wall, a first side of the cooling air cavity at least partiallydefined by an inner side surface of the first side wall, and a secondside of the cooling air cavity at least partially defined by an innerside surface of the second side wall; and an impingement air insertdisposed within the cooling air cavity, the impingement air insertcomprising a first wall complementary in shape to the portion of theinner side surface of the first side wall that at least partiallydefines the first side of the cooling air cavity, a second wallcomplementary in shape to the portion of the inner side surface of thesecond side wall that at least partially defines the second side of thecooling air cavity, and a plurality of impingement holes formed in thefirst wall and the second wall of the impingement air insert, theplurality of impingement holes oriented and formed to direct multiplediscrete jets of air onto the portion of the inner side surface of thefirst side wall that at least partially defines the first side of thecooling air cavity and the portion of the inner side surface of thesecond side wall that at least partially defines the second side of thecooling air cavity.
 19. The panel fuel injector as in claim 18, whereinthe impingement air insert is upstream of the cool side surface of thefirst side wall and the cool side surface of the second side wall, andwherein the impingement air insert is downstream of a high air pressureregion within the cooling air cavity.
 20. The panel fuel injector as inclaim 18, wherein the impingement air insert forms a gap between thecool side surface of the first side wall and a high air pressure regionwithin the cooling air cavity and forms a gap between the cool sidesurface of the second side wall and the high air pressure region withinthe cooling air cavity.